title: The progression of small-follicle reserves in the ovaries of wild African elephants (Loxodonta africana) from puberty to reproductive senescence.
abstract: This study aimed to determine whether the follicle reserve in the ovary of the African elephant declines progressively after puberty and whether its depletion constrains the fertility of older females. Elephant ovaries were fixed in 4% neutral buffered formalin and small-follicle counts made using stereological protocols. Excepting a slight rise in small-follicle numbers between 16 and 25 years of age, there was a trend for follicle numbers to fall from puberty to 70 years. Reproductive status did not impact significantly on small-follicle numbers (P=0.31). The number of early primary follicles, initially higher in number than true primary follicles, fell from post-puberty to nil at 45 years of age. Six of the seven oldest animals in the study showed signs of recent ovarian activity in the form of antral follicles, corpora lutea or large corpora nigra. The four oldest elephants (mean age 69 years) had a median small-follicle count of 11,113. In summary, it appears that the elephant ovary is capable of supplying oocytes for ovulation right up to the time of death at the age of maximum life expectancy, although the follicle reserve becomes depleted in some older elephants.
authors.affiliation: The Elephant Research and Conservation Unit, Savé Valley Conservancy, c/o 490 Borrowdale Brooke, Harare, Zimbabwe.
authors.forename: F J
authors.initials: FJ
authors.lastname: Stansfield
authors.forename: J O
authors.initials: JO
authors.lastname: Nöthling
authors.forename: W R
authors.initials: WR
authors.lastname: Allen
mesh_terms: D000818:Animals; D000835:Animals, Wild / Q000254:growth & development / Q000502:physiology*; D003338:Corpus Luteum / Q000166:cytology / Q000254:growth & development / Q000473:pathology; D004606:Elephants / Q000254:growth & development / Q000502:physiology*; D005260:Female; D007774:Lactation; D003341:Luteolysis; D009866:Oogenesis; D006080:Ovarian Follicle / Q000166:cytology / Q000254:growth & development* / Q000473:pathology; D010053:Ovary / Q000166:cytology / Q000254:growth & development / Q000473:pathology; D010784:Photomicrography; D011247:Pregnancy; D016649:Primary Ovarian Insufficiency / Q000473:pathology / Q000503:physiopathology / Q000662:veterinary; D012720:Severity of Illness Index; D046468:Sexual Development; D015030:Zimbabwe